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  • A random regression model in analysis of litter size in pigs
    Luković, Zoran ...
    Dispersion parameters for number of piglets born alive (NBA) were estimated using a random regression model (RRM). Two data sets of litter records from the Namščak farm in Slovenia were used for ... analyses. The first dataset (DS1) included records from the first to the sixth parity. The second dataset (DS2) was extended to the tenth parity. Four sow genotypes were included: Swedish Landrace (SL), Large White (LW) and their crossbred lines. The fixed part of the model included sow genotype, mating season (as month-year interaction), parity and weaning to conception interval as class effects. The age at farrowing was modelled as a quadratic regression, nested within parity. The previous lactation length was fitted as a linear regression. Random regressions for parity on Legendre polynomials were included for direct additive genetic, permanent environmental and common litter environmental effects. Orthogonal Legendre polynomials from the linear to the cubic power were fitted. Estimates of heritability ranged from 0.09 to 0.14. The ratio of permanent environmental variance to total variance increased along the trajectory from 0.05 to 0.16. Magnitudes of common litter effect were generally small (0.01 to 0.02). The eigenvalues of covariance functions showedthat between 10 and 15% of genetic variability was explained by the individual genetic curve of sows in the DS2. This proportion was mainly covered ba linear and quadratic coefficients.
    Vir: South African journal of animal science. - ISSN 0375-1589 (Letn. 34, št. 4, 2004, str. 242-248)
    Vrsta gradiva - članek, sestavni del
    Leto - 2004
    Jezik - angleški
    COBISS.SI-ID - 1656200

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